This paper studies the usage of the GPU as a collection of
groups of related processing units, where each group

communicates in some way to complete a
computation efficiently and effectively. In particular, we use the GPU to
perform jump flooding to pass information among groups of processing units in
the design of two simple real-time soft shadow algorithms. These two algorithms
are purely image-based in generating plausible soft shadows. Their computational
costs depend mainly on the resolution of the shadow map or the screen. They run
on an order of magnitude faster than existing comparable methods.

The jump flooding process of JFA-E algorithm in generating
soft shadows for the bunny: From left to right: step length equals to 32,
16, 8, 4, 2, 1 respectively. The right most picture is the final image. (click
pictures to enlarge them)

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The jump flooding process of JFA-L algorithm in generating
soft shadows for the bunny: The left most picture shows the boundary in
shadow map. The six pictures in the middle shows the process of penumbra
generation with step length equals to 32, 16, 8, 4, 2, 1 respectively. The right
most picture is the final image. (click pictures to enlarge them)